Student in Hell sinned at the outset: this fans flames (7)
I believe the answer is:
bellows
'fans flames' is the definition.
The definition and answer can be both to do with communicating as well as being verbs in their -s form.
Maybe you can see an association between them that I can't see?
'student in hell sinned at the outset' is the wordplay.
'student' becomes 'l' (learner, as in L-plates for learner drivers).
'in' is an insertion indicator.
'hell' becomes 'below' (I can't justify this - if you can you should believe this answer much more).
'at the outset' says to take the initial letters (the outset is the beginning).
The initial letter of 'sinned' is 's'.
'l' going inside 'below' is 'bellow'.
'bellow'+'s'='BELLOWS'
'this' is the link.
Can you help me to learn more?
(Other definitions for bellows that I've seen before include "Device that blows a strong current of air" , "Instrument for creating a stream of air" , "Device supplying an organ with air" , "Roars at part of the organ" , "Shouts; an air-pump" .)